The present invention relates to a waterproof fabric having a high moisture permeability. Particularly, it is concerned with a novel waterproof fabric having a high moisture permeability and permitting a quick permeation therethrough of not only gaseous sweat caused by insensible perspiration but also liquid sweat caused by sensible perspiration.
Heretofore, various fabrics have been known as moisture-permeable waterproof fabrics, such as urethane wet-coated fabric and fabric with a microporous film of polytetrafluoroethylene laminated thereto. However, since these moisture-permeable waterproof fabrics are of a hydrophobic microporous structure (average pore diameter: larger than 0.2.mu.), inside moisture can permeate the fabrics only in the form of vapor. Therefore, although insensible perspiration (gaseous sweat) caused by a light exercise is allowed to permeate the fabrics, sensible perspiration (liquid sweat) cannot pass through the fabrics due to the hydrophobicity and waterproofness of the fabrics. Additionally, the pore diameter is so large that when a hydrophilic materials such as dirt from the hands or any other hydrophilic dirt is deposited on the pore interior after repeated use, the water resistance deteriorates markedly.
On the other hand, there has also been made an attempt to incorporate a hydrophilic material such as a polymer having a high water absorbability into a coating resin layer with a view to allowing liquid sweat to escape to the exterior In this case, inside moisture is merely absorbed by the polymer having a high water absorbability and does not escape to the exterior, resulting in increased weight of clothes. A further drawback is the occurrence of dropping out due to swelling of the highly water-absorbable polymer. It has also been tried to introduce a long polyol chain into the polymer molecular chain to thereby impart a hydrophilic nature to the polymer. But it is the present situation that the water absorbing performance is insufficient and the moisture permeability is low. Thus a material which permits the permeation therethrough of sensible perspiration and yet has water resistance, has not been obtained yet.